Methodology for assessing respiration and cellular incorporation of radiolabeled substrates by soil microbial communities

A method is described for determining biodegradation kinetics of both naturally occurring and xenobiotic compounds in surface and sub-surface soil samples. The method measures both respiration and uptake into cellular biomass of¹⁴C-labeled substrates. The estimation of biomass incorporation entailed removal of cells from soil particles by washing the soil with a polyvinyl-pyrrolidone/pyrophosphate solution and H₂O₂. After separation of the cells and the soil particles by centrifugation, the cells were trapped on membrane filters for liquid scintillation counting. Mass balances were easily obtained. The technique was used to measure metabolic activity in soil profiles, including unsaturated and saturated zones. First order rate constants (K₁) were in the range of 10^–3–10^–2 hour^–1 for amino acid metabolism and 10^–5–10^–4 hour^–1 for m-cresol metabolism. Saturation kinetics were observed for amino acids and m-cresol. m-Cresol K₁ values for uptake often exceeded those for respiration by greater than a factor of ten. V_max values were low (amino acids, 10¹–10² ng g^–1 hour^–1; m-cresol, 10^–1 ng g^–1 hour^–1), whereas K_m values were quite high (amino acids, 10³–10⁴ ng g^–1; m-cresol 10³–10⁵ ng g^–1). Saturation was not observed in many horizons even at 10⁵ ng g^–1 dry soil. Frequently, respiration obeyed saturation kinetics whereas uptake was first order. It is concluded that measuring only kinetics of respiration may lead to severe underestimations of biodegradation rates.     

Safety of Eplerenone for Kidney-Transplant Recipients with Impaired Renal Function and Receiving Cyclosporine A

BackgroundAnimal studies have highlighted the role of vascular mineralocorticoid receptor during Cyclosporine A-induced nephrotoxicity. Mineralocorticoid receptor antagonists could improve kidney survival but are not commonly used during renal impairment and in association with several immunosuppressive drugs due to a supposed higher risk of adverse events. We tested the tolerance of eplerenone according to its expected adverse events: hyperkalemia, metabolic acidosis, hypotension, acute kidney failure, or any other adverse event.MethodsWe conducted a single-center, prospective, open-label study in 31 kidney-transplant recipients with impaired renal function (30 and 50 mL/min/1.73m²) and receiving cyclosporine A. All patients received eplerenone 25 mg/d for 8 weeks. Serum potassium, renal function and expected adverse events were closely monitored.ResultsEight patients experienced mild hyperkalemia (>5 mmol/L), one moderate hyperkalemia (>5.5 mmol/L) and had to receive potassium-exchange resin. No severe hyperkalemia (>6 mmol/L) occurred. One acute kidney failure was observed, secondary to diarrhea. Basal serum potassium and bicarbonate were independently associated with a higher risk of developing mild hyperkalemia (>5 mmol/L) under treatment (OR 6.5, p = 0.003 and 0.7, p = 0.007, respectively). A cut-off value of 4.35 mmol/L for basal serum potassium was the best factor to predict the risk of developing mild hyperkalemia (>5 mmol/L).ConclusionsUntil eGFR falls to 30 mL/min/1.73m², eplerenone could be safely given to kidney-transplant recipients receiving cyclosporine A, if kalemia is closely monitored. When renal function is impaired and if basal kalemia is >4.35 mmol/L, then clinicians should properly balance risk and benefit of eplerenone use and offer dietary advice. An adequately powered prospective randomized study is now needed to test its efficiency (and safety) in this population.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01834768","term_id":"NCT01834768"}}NCT01834768     

The molecular evolution of four anti-malarial immune genes in the <Emphasis Type="Italic">Anopheles gambiae</Emphasis> species complex

Background  

If the insect innate immune system is to be used as a potential blocking step in transmission of malaria, then it will require targeting one or a few genes with highest relevance and ease of manipulation. The problem is to identify and manipulate those of most importance to malaria infection without the risk of decreasing the mosquito's ability to stave off infections by microbes in general. Molecular evolution methodologies and concepts can help identify such genes. Within the setting of a comparative molecular population genetic and phylogenetic framework, involving six species of the Anopheles gambiae complex, we investigated whether a set of four pre-selected immunity genes (gambicin, NOS, Rel2 and FBN9) might have evolved under selection pressure imposed by the malaria parasite.     

Immunocytochemical localization and circadian variations of serotonin and N-acetylserotonin in photoreceptor cells. Light and electron microscopic study in the teleost pineal organ

Using two immunocytochemical procedures (i.e., immunofluorescence and the unlabeled peroxidase-antiperoxidase method), the localization of a serotonin(HT)-like and of a N-acetylserotonin (aHT)-like immunoreactivity in the pineal organ of the pike was studied during winter. It was shown that immunostaining was exclusively restricted to the cells of the receptor line (CRL = typical and modified photoreceptors). The intensity of the reactions varied through the light-dark cycle, HT-like immunoreactivity being high during the photophase and low during the scotophase. In contrast, aHT-like immunoreactivity was highest at the beginning of the scotophase. HT and aHT-like immunoreactivities were detected in all cell types of the pineal epithelium after administration of a monoamine oxidase inhibitor. Up to now, only HT immunoreactivity could be localized at the ultrastructural level. In a number of typical and modified photoreceptors, a HT-positive staining seemed to be confined within the hyaloplasm of the inner segment, particularly with that of the perikaryon and basal pedicle. Our previous and present results strongly suggest that indole compounds, which are involved in the regulation of various neuroendocrine processes in fish, are synthetized within the CRL. Taking into account that the CRL of the pike are also photosensitive, it appears more and more likely that they are photoneuroendocrine cells involved in mediating the effects of the photoperiod on various physiological and behavioral processes.     

Invasive species contribute to biotic resistance: negative effect of caprellid amphipods on an invasive tunicate

As the number of introductions of non-indigenous species (NIS) continues to rise, ecologists are faced with new and unique opportunities to observe interactions between species that do not naturally co-exist. These interactions can have important implications on the invasion process, potentially determining whether NIS become widespread and abundant, survive in small numbers, or fail to establish and disappear. Although many studies have naturally focused on the interactions between NIS and native species to examine their effects and the biological resistance of the recipient community to invasion, few have examined the effects that NIS have on each other. In some cases, interactions can facilitate the invasion process of one or both species (i.e., “invasional meltdowns”), but competition or predation can lead to negative interactions as well. The introduction of the vase tunicate, Ciona intestinalis, in Prince Edward Island (Canada) has harmed mussel aquaculture via heavy biofouling of equipment and mussels. Through both a broad-scale survey and small-scale field experiments, we show that Ciona recruitment is drastically reduced by caprellid amphipods, including the NIS Caprella mutica. This study provides an exciting example of how established invasive species can negatively impact the recruitment of a secondary invader, highlighting the potential for non-additive effects of multiple invasions.     

To be or not to be: postcubital vein in insects revealed by microtomography

To better understand insect evolution, fossils – mainly known by their wings – must be used as terminals in phylogenetic analyses. Such analyses are, however, rarely performed because of a lack of consensus on the homology of venation in insects. Researchers do not agree with the current concept on the exact number and identity of the main veins. Here, we confirm the presence, which has been in question since the early 20th century, of an independent main postcubital vein (PCu vein) between the cubital and anal veins (29 fossil and extant examined orders; > 85% of observed insects). The PCu vein corresponds to the so-called vein 1A or first anal vein. It is easily identified by the unique shape of its bulla. It may have several branches and be partially fused with the cubital and anal veins. Once the PCu vein was identified, we reconsidered as an example the particular case of the Phasmatodea, showing that extant stick insects have a unique venation among insects, with a reduced median vein and a simple cubital vein adjacent or fused to the PCu vein. This study is a new approach towards resolving wing vein homology issues, crucial for future large-scale phylogenetic analyses in insects combining extant and extinct taxa.